[ALBATTROSS]

Hello all,

In Fluent for unsteady formulation FLUENT uses implicit time discretization and the FLUENT guide says they use iterations between two time steps so they have Max Iterations / Time Step as an input. My questions is this iteration is done on the coupling between u & p? they update u and p, n times (number of iterations) in each time-step and then move on to another time step?

Thank you

[LuckyTran]

Originally Posted by ALBATTROSS

My questions is this iteration is done on the coupling between u & p? they update u and p, n times (number of iterations) in each time-step and then move on to another time step?

The short answer to your question is probably yes. The coupling between u & p is determined by your pressure-velocity coupling algorithm (SIMPLE,PISO,COUPLED,etc. or other if you are using a density-based solver). A more politically correct answer is that it's the number of times the implicitly under-relaxed equations has been solved (which can also include energy equation, phase equations, and many other equations in addition to just u & p).


An implicit temporal discretization gives a system of linear equations which in principle can be solved exactly (not requiring any iterations). However, fluent also uses implicit under-relaxation (which requires several sweeps/steps/iterations to converge to the desired time-step).